Various aerospace applications demand the use of superalloys due to their mechanical strength and creep resistance at elevated temperatures. For example, superalloys are incorporated into various structural components of aircraft, particularly structural components exposed to elevated temperatures, as well as in aircraft engines (e.g., turbine blades).
The nickel-based superalloy Inconel 625 is one of the more commonly used superalloys for high temperature aerospace applications. Inconel 625 includes nickel (Ni) as the primary alloying element, with additions of chromium (Cr), molybdenum (Mo) and niobium (Nb), among other possible elements. Because nickel is relatively heavy as compared to other common primary alloying elements (e.g., titanium (Ti)), Inconel 625 is relatively dense, thereby compromising its strength-to-weight ratio.
For even higher temperature aerospace applications, the niobium-based alloy C-103 is commonly substituted for Inconel 625. C-103 includes niobium (Nb) as the primary alloying element, with additions of hafnium (Hf) and titanium (Ti). However, C-103 is also relatively dense and has less strength than Inconel 625.
Thus, the high temperature alloys presently available for structural applications offer strength, but at the expense of significant weight. With the current mature state of single-principle-element alloy systems, a 10 to 15 percent increase in specific strength is considered difficult to achieve and generally not cost effective.
Accordingly, those skilled in the art continue with research and development efforts in the field of alloy compositions.